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Free port tool·TCP scan of 23 common ports

Check if any port is open

Run a free open port checker on any public host: scan 23 common ports, test port forwarding, and see open, closed or filtered results instantly — no signup needed.

Live TCP connect
Public hosts only
Enter a host to check its open ports.
Try google.com, github.com, or your own server.
What you get

A full port scan, without the terminal

Test connectivity the way the internet sees it — from outside your network.

23 common ports

Scan the 23 ports that matter most — 80, 443, 21, 22, 25 and more — or check a single custom port for the service you run.

Port forwarding tester

Confirm your router actually forwards traffic to your machine — essential for game servers, cameras and self-hosted apps.

Open, closed or filtered

Each port is reported as open, closed or filtered, so you know whether a service is reachable, refused, or blocked by a firewall.

Public hosts only

The checker tests public hosts from the outside — the same view a visitor or attacker has — so nothing inside your network is probed.

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FAQ

Open port checker FAQs

Enter the hostname or IP and the port number, then run the scan. The checker attempts a TCP connection from outside your network and reports the port as open, closed, or filtered in seconds. It works on any public host with no signup required.
A closed port means the host was reachable but refused the connection — nothing is listening there. A filtered port means no response came back, usually because a firewall dropped the traffic. Filtered suggests stealth; closed confirms the host is up but the port is inactive.
Set up the forwarding rule on your router, start the service on your machine, then scan your public IP and the forwarded port here. If it shows open, traffic is reaching your service. If it shows closed or filtered, recheck the router rule, the local firewall, and the machine's IP address.
The 23 common ports cover the services people check most — web (80, 443), email (25, 110, 143, 587), file transfer (21, 22) and databases (3306, 5432) among them. For anything else, scan a custom port number to test your specific service.
Locally reachable but externally closed usually means your router isn't forwarding the port, your ISP is blocking it, or a firewall drops outside traffic. This checker shows what the internet sees — which is the view that matters for remote access.
Scanning your own public IP or a host you control is standard diagnostics and safe. Don't scan hosts you don't own without permission — many providers treat unsolicited scans as hostile. This tool only checks the public host you enter.